Method and apparatus for preventing armature-coil heating



April 14, 1925.

. C. LE G. FORTESCUE METHOD AND APPARATUS FOR PREVENTLNG ARMATURE COIL HEATING Filed Aug. 8, 1919 WITNESSES ATTORNEY Patented 14, 1925i.

UNITE ST ATES CHARLES LE Gr. FORTESCUE, OF PITTSBURGH, EENNSYLVNIA, ASSIGNOR TO WEST- INGHO'USE ELECTRIC @t MANUFACTURING COMPANY, A CORPORATION 0F PENN- SYLVANIA.

IHETHOD AND APPARATUS FOR PBEVENTING ARMATURE-COIL HEATING.

Application filed August 8,1919. Serial No. 316,089.

To all whom it may concer/n.'

Be it known that I, CHARLES LE G. Fon- TnscUE, a citizen oi the United States, and a resident of Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Methods and Apparatus for Preventin Armature-Coil Heating, of which the tollowing is a speciication.r Y

My invention relates to commutator dynamo-electric machines, and it has for its object to provide a method and apparatus, in connection with machines of the character designated, which shall prevent the continual short circuiting ot any one armature coil during the time that the armature winding is at standstill but energized with full-load voltage.

Inorder to more fully understand my invention, reference ymay be had to the accompanying drawing invwhich Figure 1 is an end elevational view of a machine aggregate embodying my invention, and Fig. 2 is a side view, partially in section and partally in elevation, ot the machine shown in `Fig. 1. y

lVhen machines of the character described are used for certain purposes, especially when employed as propulsion motors tor electric railway vehicles, it isV necessary that they be able to furnish full torque or'withstand ull-load voltage :tor a predetermined period, although, during that period, the armature or rotating element of the machine is maintained stationary. In the past,'this requirement has frequently led to severe overheating of that armature coil which happens to be short circuited by the brushes during the standstill period, and it is the Yobjectct my invention, therefore, to provide means, in connection with a commutator machine which must undergo the above test, to prevent this continual short-circuitf ing of any one armature coil.

I propose to make the iield frame of the commutatcr machine in suchy manner that it may be rotated very slowly during the time that the normally rotatable armature winding is stationary. Inasmuch as the brush rigging is attached rigidly to the iield frame in such manner that the brushes are always inthe correct position with respect to thefield of the machine, they are also moved simultaneously with the field frame in such manner that successive coils are short circuited in the armature winding. By so arranging a dynamo-electric machine of the character described, I find that the excessive overheating which may be occasioned in fulg iilling the above requirement during standstill is eliminated, and the heating is, moreover, more equally distributed in the various coils of the armature winding.

Referring more particularly to the drawing, a base l, upon which are mounted supporting members 2 and 3, is shown. Journal members 4 and 5 are cast integrally with the supports 2 and 3, respectively, and are adapted to receive a shaft 6 upon which a normally rotatable armature winding 7 and associated commutator cylinder 7a are mounted. A motor casing 8 is provided, at each end, with portions 9 and 10 which are exteriorly journaled about extended portions of the'inembers 4 and 5, thus adapting the casing for independent rotary movement about the armature widing 7. Field-magnet pole pieces l1 and 12 are rigidly attached to the casing 8 and have iieldwindings 13 and 14 respectively applied thereto. Brush holders 15 and 16 are likewise rigidly attached to the casing 8 and, therefore, move simultaneously therewith, and carry brushes 17 and 18, respectively, around the comm utator 7. Y

Pinioned to the portion 9 of the casing 8 are slip rings 19 and 20 to which are attached leads 21 and 22 respectively connecting the slip rings to the 'field-pole windings 13 and 14, thus furnishing means whereby the latter may be energized, even though the entire iield frame is being rotated. VIt will be noted that I have not shown the electrical connections to thebrushes or any brushes bearing upon the slip rings 19 and 20 and the connections whereby the field windings .are energized. It will be understood that any means of effecting the electrical connections between the various members may be'used. i. f

A gear wheel 23 is rigidly attached to the casing 8 and is'meshed with a worm wheel 24 which is driven by an auxiliary motor 26. A bracket member 27 provides a support for the motor 26.

Having described a dynamo-electric masition with respect to the field iiux.

chine constructed in accordance with my invention, the operation thereo't is as follows:

Assuming that the shaft 6 is attached to non-moving` load, and, moveover, assumingthat full voltage is applied to the brushes, it is necessary that the relative positions of the brushes and the armature coils shall be continually changed in order to prevent that coil which happens to be short circuited when the full. voltage is applied to the armature winding;` from being` burned out. Any suitable switching means may be provided to insure the automatic starting of the motor` 26 at the time the voltage is applied to the armature winding; 7 or the switching' operations maj.'v be performed by hand. rflic iield trame will then be slowly rotated through the medium olf the worm wheel Q5 and associated gear wheel 23, it being remembered that the latter is rigidly attached to thc easing- 8. inasmuch as the brushes l5 move simultaneously with Ythe field frame, no one armature coil will remain short circuited for any length of time, and, moreover, it is further to be noted that the brushes will always be in the corr-ect po- Suitable electrical connections between the iield windings and the slip rings 19 and 2O will insure the 'proper energization oit the iield windings 13 and 14, even though the casing` 8 is being moved rotarily.

Any means may be employed whereby, upon the armature winding 'i' attaining a predetermined speed, the .motor 26 may be stopped. In particular, a centritugally operated switch may be employed to perform thisl operation., or the switch may `be opened by an attendant. Then the motor 26 stops, the large di'lierence in pitch between the worm wheel 25 and the gear wheel 23 meshing therewith, will provide a locking action, 'and the casing 8 will be maintained stationary during the time that the armature winding 7' is rotating in a normal manner.

As a concrete example of a switching mechanism for accomplishing the results hereinbetore mentioned, l have shown a supply-line comprising conductors 36 and 31 lior energizing the main motor through brushes bearing; uponthe sli-p rings 19 and 20. A controller 32 is shown for starting and stopping` the main motor. Connected across the brushes of the slip rings 19 and 2O is a circuit containing the smalfl ausiliari,v motor 26 and a centrifugal switch which is geared to the shaft 6 of the main motor, shown. In this manner, whenever the controller 32 is operated to start the main motor, the auxiliary motor 26 is also started', but when the speed oi the main motor reaches a predetermined value, the cent-ritugal switch 33 operates to open the circuit ot the auxiliary motor, as hereinbe'tore described,

`While l have described but one embodiment ci my invention, it apparent that many modifications therein may occur to those skilled in the art, and l desire, theretore., that it be limited only by the scope ot the prior art or speciiically set forth in the appended claims.

l claim as niy invention:

l. in a dynamo-electric machine, a normally rotatable torque-producing member7 a normally member, and means actuated in accordance with the starting conditions ot said machine tor moving the normally stationary member.

The combination ot a ccmmutator-type l.j \,fna.;ioelectric machine having a normally stationary member and a rotatable torqueproducinfaT member, toraue-transmitting .means associated with said torque-producing member, and means 'for slowly moving said normally stationary4 member when the torque produced in said torque-producing member is insuiiicient to rotate said member against its load.

The method oi"- preventing unequal armature heating oit an electric motor producing torque atstandstill which cons-ists in causing the normally stationary member to rotate when the torque produced in the rotating member is insufficient to rotate said member against its load.

i. VThe method of ,operating a commutatoretype electric motor which consists in energizing said motor to produce a torque at standstill and in causing different coils to he successively short-ci-rcuited while the torque-producingmember is stationary.

The method of operating a dynamoelect-ric machine having a normally rotatable arn'iature ndnding` and a normally sta- 'tionaryv held-pole iframe, which consists in moving the lield iframe while the armature winding,` is stationary, and in locking the field 'trame in a stationary position when said armature winding` moves at a p-redetei mined speed.

ln a comnfiutator dynamo-electric machine, a normally rotatable armature windprovided with a commutator vmember and brushes bearing thereupon, a normally stationary field-pole 'frame provided with a gear w reel rig-idly secured thereto, and driving means for said wheel whereby the field trame may be slowly rotated, said driving means constituting' a loch for the vlield trame under predetermined conditions.

T. in a connnutator dynamo-electric machine, a normally rotatable armature winding provided with a commutator member and brushes bearing thereupon, a normally stationary field-pole trame provided with a gear wheel ridly secured thereto, an yauxiliary motor ior rotatingsaid Vlield frame, and means whereby the latter is locked into position when the auxiliary motor stops.

8. In a commutator dynamo-electric machine, a normally rotatable armature winding provided with a commutator member and brushes bearing thereupon', a normally stationary field-pole frame provided with a gear wheel rigidly securedthereto, and an auxiliary motor for said field frame and carrying a Worm meshing with said gear wheel, whereby the field frame is locked in position when the auxiliary motor stops.

9. In a commutator dynamo-electric machine, a normally rotatable armature Winding provided with a commutator member and brushes bearing thereupon, a normally stationary field-pole frame provided with a gear wheel rigidly secured thereto, and an auxiliary motor for said field frame and carrying a worm meshing with said gear wheel, whereby the field frame is locked in position when the auxiliary motor stops, and means whereby the lield windings may be properly energized during theirrotary movement.

l0. In a oommutator dynamo-electric motor, means for preventing the continual short eireuiting of any one coil in said m0- tor when the torque is insuificient to overcome the stand-still resistance of the load, and means whereby said first means may be rendered ineiective after the motor has attained a predetermined speed.

11. The method of operating an alternating-current eommutator motor which consists in energizing sai-d motor to produce a torque against a mechanical load, and in causing different coils to be successively short-circuited while said load is stationary.

In testimony whereof, I have hereunto subscribed my name this 30th day of Ju1y v CHARLES LE G. FORTESCUE. 

